The present invention refers to an apparatus for sorting constituents of a mixture according to density and/or grain size, and in particular to a sorting apparatus of a type including an inclined vibratory table which is driven by crankshafts and arranged underneath a feed inlet.
In a conventional apparatus of this type, the entire work area is driven by two crankshafts, with several work tables arranged side-by-side in conveying direction and operated at a phase shift relative to each other. A sorting apparatus of this type achieves only a limited separation effect because the arrangement of only a single work table, which extends over the entire conveying path and evenly shakes the material, results only in an even and uniform treatment of the particles being separated.
The European patent application EP-A1 396 529 describes a separating device which operates by vibration and uses several inclined vibrating separating areas which are arranged successively to each other. The separation is significantly influenced by the direction of the vibration which causes different movement patterns of individual small grained constituents.
German patent application DE 3 306 769 describes a separating device for agricultural products, which includes a rotating drum. The unsorted mixture of products and other material is transported by a conveyor and exits the conveyor in such a manner that the drum surface is impacted at a certain angle relative to the horizontal. The separation effect is essentially influenced by the area of impact upon the drum surface and by the various impact forces exerted by the constituents, with the principal separation effect being obtained through conversion of a force vector component from the separating device onto the constituents of the material. The shape and specific weight of the material are secondary for purposes of separation.
German publication DE 3 804 190 describes an apparatus for classifying a material flow, in particular to remove hard particles from compost fractions. The classifier includes four rotating drums which are arranged above each other in the form of a steep staircase, with the compost being fed to the uppermost drum. The separation effect is attained, like in the previously described German publication DE 3 306 769, through rotation of the drums, with hard particles being laterally deflected from the surface of the drums while softer materials adhere to the rotating drums and exit on the other side thereof. Thus, the separation effect is attained through different adherence of the particles to the surface of the drums.